(1) Field of the Invention
The present invention relates to the field of extrusion and more particularly to the field of extruded foam structural shapes.
(2) Description of the Related Art
Low gravity forming of metals is normally accomplished with a mold within a furnace so that only small specimens can be made. A number of patents have to do with forming metal foams.
U.S. Pat. No. 3,005,700 discloses a process of producing foamed metal by melting a metal, continuously introducing it into a reaction chamber by gravity flow, continuously introducing a solid state thermally decomposable foaming agent into the reaction chamber and intermixing the metal and foaming agent in the reaction chamber. The foaming agent is decomposed by the heat of the metal to cause foaming of the metal. The foamed metal is expelled from the reaction chamber by expansive force of metal foaming in the chamber. Then the transferred metal then is allowed to cool to provide solidified foam metal product.
U.S. Pat. No. 3,647,924 discloses an electrically powered furnace for melting high-melting point materials in the vacuum and zero gravity environment of space comprising an alumina crucible, cylindrical in shape, and enclosing a cylindrical tantalum sample holder that contains the sample to be melted. The crucible is surrounded by concentric cylindrical enclosures made of polished sheet molybdenum. The sample holder is clamped between a pair of round plates and a pair of alignment bolts are joined to the circular plates and extend along the longitudinal axis of the furnace through the end covers of the crucible and surrounding concentric enclosures.
U.S. Pat. No. 3,941,182 discloses steel wires are pulled through a reactor tube in which they continuously interact with a foaming metal mass. The steel wires are coated with a metal which forms a binary alloy with the matrix metal, thereby protecting the steel from being dissolved. The foaming matrix metal is usually aluminum alloy but can be any light or low melting metal including zinc or lead. The steel wires protect the metal foam from cracking in the pultrusion process.
Patent Number 4,677,642 discloses an electron bombardment furnace (B) which consists of two confinement grid sections (26, 28) which may be moved and separated from each other. Inside the bombardment furnace, a tungsten element (14) is enclosed. The material specimen (18) is located within the tungsten element and grounded by means of grounded support wires (20, 22) connected to the respective sections of the furnace. The material specimen (18) is supported on the ground wires and heated by electron bombardment until melt occurs. The furnace sections are separated in opposite directions causing the ground wires to pull from the surfaces of the specimen, leaving the specimen freely suspended in the process chamber without the action of external forces. The specimen remains in its melt condition in the processing chamber where it can be undercooled without external forces acting on the specimen, which would cause dynamic nucleation.
U.S. Pat. No. 4,168,182 discloses a shaped metal base component being formed, such as by casting or forging. The component is then thinly coated with a material, such as a ceramic material, having a higher melting point than the material of the shaped component. The coated component is then heated under zero gravity conditions up to a temperature which is below the melting point of the coating, but which is high enough to soften the component, the coating maintaining the shape of the component during the heating step. After completion of the heating step, the coated component is cooled under zero gravity conditions. The forming and coating of the component take place on earth, and the steps of heating and cooling the coated component are performed in space. After cooling the coated component, the coating is either stripped off the component or left on the component to form an integral part of the shaped body.
U.S. Pat. No. 4,314,835 discloses an improved article made of foamed glass or similar materials and method of manufacture. Thus, a construction panel may be formed to bear weight, withstand weather and take reasonable impact and abuse, because of a tempered outer skin supported inside by a skeletal network of solid, poreless material formed about low density pockets of substantially constant size and frequency. These panels are made by continuous pulling of the panels through a heat controlled mold in contact with the surface skin from a continuously fed molten mass into which is injected from the bottom size and frequency controlled foaming agents or gaseous bubbles which rise in the molten mass to a position where they are frozen in place.
U.S. Pat. No. 4,480,677 discloses an apparatus and methods whereby materials may be processed and formed in space utilizing the special conditions of space to great advantage. More specifically, methods and apparatus are presented which vaporize substances on a variety of forms. The processing steps required are: a. heat a material (not necessarily a metal) to form a vapor; b. direct the vapor, and c. deposit the material on a form. To provide the energy required for this process, sunlight is concentrated by a mirror, directed through an aperture, converted to heat by absorption, and the heat conducted to a cavity where metals such as steel or aluminum, are vaporized. The metal is fed into the cavity in the form of a rod. The resultant metal vapors are expanded through a nozzle and directed to a temperature controlled inflated form which may be rotated in the path of the metal vapor beam. This fabrication method seems particularly well suited for forming seamless pressure vessels on inflated forms, or flat surfaces on endless belts, but is not limited to such shapes and forms. Objects with complex internal structure may be formed provided the surfaces are locally flat or have smooth curves. The metallurgy of vapor deposited metals in particular is well understood and a large number of patents (see for example Cole, U.S. Pat. No. 3,690,333) have been obtained in this field for the use of vapor deposition for coating substrates.
U.S. Pat. No. 4,973,358 discloses a method for producing foamed metal in which gaseous bubbles are retained within a mass of molten metal during foaming. The method comprises heating a composite of a metal matrix and finely divided solid stabilizer particles above the liquidus temperature of the metal matrix, discharging gas bubbles into the molten metal composite below the surface thereof to thereby form a foamed melt on the surface of the molten metal composite and cooling the foamed melt thus formed below the solidus temperature of the melt to form a solid foamed metal having a plurality of closed cells.
U.S. Pat. No. 6,263,953 discloses a continuous casting method comprising the following steps: a) the material is melted and a continuous strand formed from said material; b) the material strand is cooled or left to cool so that at least a part thereof has a temperature at which its structure is pasty; c) gas is introduced into that part of the material strand which has a pasty structure so as to form hollow cavities, the material strand being moved from the top towards the bottom; and d) the material is left to solidify. The invention also relates to a device for carrying out this method.
U.S. Pat. No. 6,508,854 discloses a method of preparing a magnetostrictive material, including the steps of: (a) forming a melt of metals having a composition corresponding to the magnetostrictive material; (b) subjecting the melt to a micro-gravity environment; and (c) cooling the melt in the micro-gravity environment at a rate of at least 50° C. per second, while applying a magnetic field to the melt, to solidity the melt.
U.S. Pat. No. 6,889,744 discloses an apparatus and a method for foaming a hollow profile with metal foam. The device comprises induction means, into which the hollow profile can be introduced, in which a foamable raw material is disposed, the hollow profile having an electrical interruption, which extends in its longitudinal direction of the hollow profile, and being in contact with the induction means at least at one place, so that, during the inductive foaming of the raw material, the (56) References Cited hollow profile forms part of the induction means.
U.S. Pat. No. 6,930,304 discloses a process and apparatus for separating element isotopes in a microgravity or low-gravity environment using electromagnetic radiation, e.g., sunlight, to heat and ionize a stream of raw materials, followed by electromagnetic separation, and collection of the desired isotopes in or on one or more collection surfaces or receptacles, such as a rotating surface. A cylindrical mirror can serve to collect and concentrate the electromagnetic radiation, permitting the stream of material to be heated and ionized while the path of the stream of material is oriented other than parallel to the direction of the radiation.
None of the above listed patents describe an orbital foam extrusion apparatus or process that rotates to produce 1 g conditions. Development of an orbital foam extrusion apparatus and process which can rotate to produce 1 g conditions represents a great improvement in the field of space construction and satisfies a long felt need of the space construction engineer.